Abstract

Post annealing is frequently used for improving the device performance of the kesterite solar cells. The rise in the efficiency has been mainly attributed to elemental interdiffusion such as Na, Cd, Cu, and Zn[1]–[3]. In particular, at the CdS/CZTS interface, the interdiffusion between Cd and Zn was shown to reduce the conduction band offset resulting in a more favourable band alignment[2]. In the bulk, the Cu-Zn disorder and Na diffusion are affecting the device parameters[1], [3]. A drop in the efficiency occurs at an annealing temperature higher than 300℃ and/or longer annealing times[2]. Since most studies on post annealing were carried out on complete celIs, it is difficult to assess which effects are responsible for the performance behaviour. In order to decouple the different contributions, we have performed systematic studies at three different stages during sample fabrication. We studied the effect of post annealing on the CZTS absorber, CZTS/CdS heterojunction, and CZTS/CdS/Al:ZnO complete device. The post annealing was carried out in nitrogen atmosphere in a temperature range varying from 125℃ to 325℃. The efficiency of the complete cells increases at a temperature as low as 150℃, and it drops above 300℃. Our findings reveal a band to band (BB) photoluminescence (PL) emission from annealed CZTS/CdS and complete devices which did not occur when annealing only the CZTS absorbers. Additionally, BB PL position and bandgap derived from EQE measurements correlate with each other. The BB PL peak reaches a maximum for solar cells annealed at 275℃, which coincides with the lowest VOC deficit (see Figure 1 a, b). The BB emission has been reported previously in CZTS polycrystalline powders at room temperature[4]. We will discuss the effect of post annealing in terms of efficiency and BB emission by comparing post annealing at different stages.
Original languageEnglish
Publication date2019
Number of pages1
Publication statusPublished - 2019
Event10th European Kesterite+ workshop - Uppsala University, Uppsala , Sweden
Duration: 20 Nov 201922 Nov 2019
Conference number: 10

Conference

Conference10th European Kesterite+ workshop
Number10
LocationUppsala University
CountrySweden
CityUppsala
Period20/11/201922/11/2019

Cite this

@conference{800a7453ec714a2d9e04e1867d87cba6,
title = "Band to band photoluminescence emission revealed in post annealed Cu2ZnSnS4 solar cells",
abstract = "Post annealing is frequently used for improving the device performance of the kesterite solar cells. The rise in the efficiency has been mainly attributed to elemental interdiffusion such as Na, Cd, Cu, and Zn[1]–[3]. In particular, at the CdS/CZTS interface, the interdiffusion between Cd and Zn was shown to reduce the conduction band offset resulting in a more favourable band alignment[2]. In the bulk, the Cu-Zn disorder and Na diffusion are affecting the device parameters[1], [3]. A drop in the efficiency occurs at an annealing temperature higher than 300℃ and/or longer annealing times[2]. Since most studies on post annealing were carried out on complete celIs, it is difficult to assess which effects are responsible for the performance behaviour. In order to decouple the different contributions, we have performed systematic studies at three different stages during sample fabrication. We studied the effect of post annealing on the CZTS absorber, CZTS/CdS heterojunction, and CZTS/CdS/Al:ZnO complete device. The post annealing was carried out in nitrogen atmosphere in a temperature range varying from 125℃ to 325℃. The efficiency of the complete cells increases at a temperature as low as 150℃, and it drops above 300℃. Our findings reveal a band to band (BB) photoluminescence (PL) emission from annealed CZTS/CdS and complete devices which did not occur when annealing only the CZTS absorbers. Additionally, BB PL position and bandgap derived from EQE measurements correlate with each other. The BB PL peak reaches a maximum for solar cells annealed at 275℃, which coincides with the lowest VOC deficit (see Figure 1 a, b). The BB emission has been reported previously in CZTS polycrystalline powders at room temperature[4]. We will discuss the effect of post annealing in terms of efficiency and BB emission by comparing post annealing at different stages.",
author = "Mungunshagai Gansukh and Martinho, {Filipe Mesquita Alves} and Mari{\~n}o, {Sim{\'o}n L{\'o}pez} and {Espindola Rodriguez}, Moises and Engberg, {Sara Lena Josefin} and Alireza Hajijafarassar and Eugen Stamate and Ole Hansen and J{\o}rgen Schou and Stela Canulescu",
year = "2019",
language = "English",
note = "10<sup>th</sup> European Kesterite+ workshop ; Conference date: 20-11-2019 Through 22-11-2019",

}

Band to band photoluminescence emission revealed in post annealed Cu2ZnSnS4 solar cells. / Gansukh, Mungunshagai; Martinho, Filipe Mesquita Alves; Mariño, Simón López; Espindola Rodriguez, Moises; Engberg, Sara Lena Josefin; Hajijafarassar, Alireza; Stamate, Eugen; Hansen, Ole; Schou, Jørgen; Canulescu, Stela.

2019. Abstract from 10th European Kesterite+ workshop, Uppsala , Sweden.

Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

TY - ABST

T1 - Band to band photoluminescence emission revealed in post annealed Cu2ZnSnS4 solar cells

AU - Gansukh, Mungunshagai

AU - Martinho, Filipe Mesquita Alves

AU - Mariño, Simón López

AU - Espindola Rodriguez, Moises

AU - Engberg, Sara Lena Josefin

AU - Hajijafarassar, Alireza

AU - Stamate, Eugen

AU - Hansen, Ole

AU - Schou, Jørgen

AU - Canulescu, Stela

PY - 2019

Y1 - 2019

N2 - Post annealing is frequently used for improving the device performance of the kesterite solar cells. The rise in the efficiency has been mainly attributed to elemental interdiffusion such as Na, Cd, Cu, and Zn[1]–[3]. In particular, at the CdS/CZTS interface, the interdiffusion between Cd and Zn was shown to reduce the conduction band offset resulting in a more favourable band alignment[2]. In the bulk, the Cu-Zn disorder and Na diffusion are affecting the device parameters[1], [3]. A drop in the efficiency occurs at an annealing temperature higher than 300℃ and/or longer annealing times[2]. Since most studies on post annealing were carried out on complete celIs, it is difficult to assess which effects are responsible for the performance behaviour. In order to decouple the different contributions, we have performed systematic studies at three different stages during sample fabrication. We studied the effect of post annealing on the CZTS absorber, CZTS/CdS heterojunction, and CZTS/CdS/Al:ZnO complete device. The post annealing was carried out in nitrogen atmosphere in a temperature range varying from 125℃ to 325℃. The efficiency of the complete cells increases at a temperature as low as 150℃, and it drops above 300℃. Our findings reveal a band to band (BB) photoluminescence (PL) emission from annealed CZTS/CdS and complete devices which did not occur when annealing only the CZTS absorbers. Additionally, BB PL position and bandgap derived from EQE measurements correlate with each other. The BB PL peak reaches a maximum for solar cells annealed at 275℃, which coincides with the lowest VOC deficit (see Figure 1 a, b). The BB emission has been reported previously in CZTS polycrystalline powders at room temperature[4]. We will discuss the effect of post annealing in terms of efficiency and BB emission by comparing post annealing at different stages.

AB - Post annealing is frequently used for improving the device performance of the kesterite solar cells. The rise in the efficiency has been mainly attributed to elemental interdiffusion such as Na, Cd, Cu, and Zn[1]–[3]. In particular, at the CdS/CZTS interface, the interdiffusion between Cd and Zn was shown to reduce the conduction band offset resulting in a more favourable band alignment[2]. In the bulk, the Cu-Zn disorder and Na diffusion are affecting the device parameters[1], [3]. A drop in the efficiency occurs at an annealing temperature higher than 300℃ and/or longer annealing times[2]. Since most studies on post annealing were carried out on complete celIs, it is difficult to assess which effects are responsible for the performance behaviour. In order to decouple the different contributions, we have performed systematic studies at three different stages during sample fabrication. We studied the effect of post annealing on the CZTS absorber, CZTS/CdS heterojunction, and CZTS/CdS/Al:ZnO complete device. The post annealing was carried out in nitrogen atmosphere in a temperature range varying from 125℃ to 325℃. The efficiency of the complete cells increases at a temperature as low as 150℃, and it drops above 300℃. Our findings reveal a band to band (BB) photoluminescence (PL) emission from annealed CZTS/CdS and complete devices which did not occur when annealing only the CZTS absorbers. Additionally, BB PL position and bandgap derived from EQE measurements correlate with each other. The BB PL peak reaches a maximum for solar cells annealed at 275℃, which coincides with the lowest VOC deficit (see Figure 1 a, b). The BB emission has been reported previously in CZTS polycrystalline powders at room temperature[4]. We will discuss the effect of post annealing in terms of efficiency and BB emission by comparing post annealing at different stages.

M3 - Conference abstract for conference

ER -