TY - JOUR
T1 - Is Excess PbI2 Beneficial for Perovskite Solar Cell Performance?
AU - Liu, Fangzhou
AU - Dong, Qi
AU - Wong, Man Kwong
AU - Djurišić, Aleksandra B.
AU - Ng, Annie
AU - Ren, Zhiwei
AU - Shen, Qian
AU - Surya, Charles
AU - Chan, Wai Kin
AU - Wang, Jian
AU - Ng, Alan Man Ching
AU - Liao, Changzhong
AU - Li, Hangkong
AU - Shih, Kaimin
AU - Wei, Chengrong
AU - Su, Huimin
AU - Dai, Junfeng
N1 - Funding Information:
Financial support from the Strategic Research Theme, University Development Fund, and Small Project Funding of the University of Hong Kong is acknowledged. Partial support of the work was provided by the RGC Theme-based Research Scheme (Grant number: HKU T23-713/11). A.M.C.N. would like to acknowledge support from a grant from National Science Fund of China (NSFC grant number: 21403103)
Publisher Copyright:
© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
PY - 2016/4/6
Y1 - 2016/4/6
N2 - Unreacted lead iodide is commonly believed to be beneficial to the efficiency of methylammonium lead iodide perovskite based solar cells, since it has been proposed to passivate the defects in perovskite grain boundaries. However, it is shown here that the presence of unreacted PbI2 results in an intrinsic instability of the film under illumination, leading to the film degradation under inert atmosphere and faster degradation upon exposure to illumination and humidity. The perovskite films without lead iodide have improved stability, but lower efficiency due to inferior film morphology (smaller grain size, the presence of pinholes). Optimization of the deposition process resulted in PbI2-free perovskite films giving comparable efficiency to those with excess PbI2 (14.2 ± 1.3% compared to 15.1 ± 0.9%) Thus, optimization of the deposition process for PbI2-free films leads to dense, pinhole-free, large grain size perovskite films which result in cells with high efficiency without detrimental effects on the film photostability caused by excess PbI2. However, it should be noted that for encapsulated devices illuminated through the substrate (fluorine-doped tin oxide glass, TiO2 film), film photostability is not a key factor in the device degradation.
AB - Unreacted lead iodide is commonly believed to be beneficial to the efficiency of methylammonium lead iodide perovskite based solar cells, since it has been proposed to passivate the defects in perovskite grain boundaries. However, it is shown here that the presence of unreacted PbI2 results in an intrinsic instability of the film under illumination, leading to the film degradation under inert atmosphere and faster degradation upon exposure to illumination and humidity. The perovskite films without lead iodide have improved stability, but lower efficiency due to inferior film morphology (smaller grain size, the presence of pinholes). Optimization of the deposition process resulted in PbI2-free perovskite films giving comparable efficiency to those with excess PbI2 (14.2 ± 1.3% compared to 15.1 ± 0.9%) Thus, optimization of the deposition process for PbI2-free films leads to dense, pinhole-free, large grain size perovskite films which result in cells with high efficiency without detrimental effects on the film photostability caused by excess PbI2. However, it should be noted that for encapsulated devices illuminated through the substrate (fluorine-doped tin oxide glass, TiO2 film), film photostability is not a key factor in the device degradation.
KW - organometallic halide perovskite
KW - solar cells
KW - stability
KW - XRD
UR - http://www.scopus.com/inward/record.url?scp=84964624200&partnerID=8YFLogxK
U2 - 10.1002/aenm.201502206
DO - 10.1002/aenm.201502206
M3 - Journal article
AN - SCOPUS:84964624200
SN - 1614-6832
VL - 6
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 7
M1 - 1502206
ER -