Interfacial engineering strategy based on polymer modification to regulate the residual stress in CsPbI2Br based perovskite solar cells

Spring‐Like Ammonium Salt Assisting Stress Release for Low‐Temperature Deposited FAPbI3 Films Toward Flexible Photovoltaic Application

“…In order to reduce the residual stress and enhance the flexibility of perovskite, polymer materials are widely utilized. [24][25][26][27][28] However, the interfacial contact between the polymer materials and the perovskite layer is poor due to the difference of the structure, which affects the transport of carriers and the stable output of performance. Therefore, we need to find a material which can reduce the density of trap states on the surface of the perovskite film, reduce the residual stress of the perovskite layer, and have good contact with the perovskite surface.…”

Inorganic CsPbI2Br halide perovskites: from fundamentals to solar cell optimizations

“…Benefitting from these, a PCE of 16.76% (a J SC of 16.01 mA cm −2 , a V OC of 1.31 V and a FF of 0.800) along with long-term device stability was obtained for the device under investigation with 1 mg mL −1 B-CDs. 82 Meanwhile, the addition of π-conjugated molecules of bis(2-ethylhexyl) 3,30((4,8-bis (5-(2-ethylhexyl)-3,4-difluorothiophen-2-yl)benzo[1,2- b :4,5- b 0]dithiophene-2,6-di yl)bis(3,300-dioctyl[2,20: 50,200-terthiophene]-500,5-diyl))(2 E ,20 E )-bis(2-cyanoacrylate) (BTEC-2F) 19 or poly[[5,6-difluoro-2-(2-hexyldecyl)-2 H -benzotriazole-4,7-diyl]-2,5-thiophenediyl[4,8-bis[5-(tripropylsilyl)-2-thienyl]benzo[1,2- b :4,5- b ']dithiophene-2,6-diyl]-2,5-thiophenediyl] (J71) 83 at the CsPbI 2 Br/spiro-OMeTAD interface induced the formation of larger perovskite grains along with improved moisture resistance films, attributed to that BTEC-2F and J71 could assist the secondary growth of the perovskite crystal and increased hydrophobicity of the film surface. More importantly, the interaction between BTEC-2F (S and O atoms) or J71 (S and N atoms) with Pb dangling bonds in CsPbI 2 Br alleviated the microstrain between the inorganic perovskite grains, resulting in a well-preserved lattice and lower defect density of the CsPbI 2 Br film.…”

“…After modification, a PCE of 16.25% (a J SC of 16.13 mA cm À2 , a V OC of 1.29 V and a FF of 0.784) and a PCE of 15.80% (a J SC of 15.96 mA cm À2 , a V OC of 1.28 V and a FF of 0.773) with higher operational stability were achieved for the device under investigation with 0.5 mg mL À1 BTEC-2F/and 1 mg mL À1 J71, respectively. 19,83 It was found that guanidinium bromine (GABr) treatment on the CsPbI 2 Br film formed a Br-rich region of CsPbI (2Àx) Br (1+x) (0 o x o 0.5) near to the perovskite surface, which lowered the Fermi energy level and improved the energy level alignment between CsPbI 2 Br and spiro-OMeTAD. As a result, a PCE of 16.97% (a J SC of 15.90 mA cm À2 , a V OC of 1.31 V and a FF of 0.815) was attained for the device under investigation with 2.0 mg mL À1 GABr.…”

Approaching the Fill Factor Limit in Dopant-Free Hole Transporting Layer-Based All-Inorganic Perovskite Solar Cells

“…15−18 organic molecules as an interfacial modifier could induce a secondary crystallization of CsPbI x Br 3−x during thermal treatment, which suppresses the microstrain of perovskite and improves its phase stability. 19,20 Therefore, on top of functioning to extract and transport holes, π-conjugated organic molecule as HTL could also contribute to regulating the tensile stress of CsPbI x Br 3−x , which has, however, rarely studied.…”

“…In addition to thermal instability of HTL in the device, the residual tensile stress would also cause phase instability of CsPbI x Br 3– x , which has been remained as an unresolved issue. The tensile stress arises from the thermal expansion coefficient mismatch between the ITO/ZnO substrate and the perovskite. − Our previous research unveils that π-conjugated organic molecules as an interfacial modifier could induce a secondary crystallization of CsPbI x Br 3– x during thermal treatment, which suppresses the microstrain of perovskite and improves its phase stability. , Therefore, on top of functioning to extract and transport holes, π-conjugated organic molecule as HTL could also contribute to regulating the tensile stress of CsPbI x Br 3– x , which has, however, rarely studied.…”