Advancing inorganic perovskite solar cells for application in tandem architectures

Silicon-perovskite tandem solar cells have remarkable power conversion efficiencies (PCEs) and can contribute to the rapid transition towards renewable energy sources. While inorganic perovskite solar cells show superior temperature stability as compared to organic-inorganic perovskite solar cells, they have lower PCEs and lower open-circuit voltages (VOC), i.e. a higher voltage loss. In addition, a strong hysteresis in current density-voltage measurements is common and results in a reduced stabilised power output. This thesis investigates the reasons for this and presents solutions for the higher voltage loss and hysteresis in inorganic perovskite solar cells. By conducting intensity-dependent photoluminescence (PL) measurements on perovskite layers with and without each charge-selective transport layer (CTL), the contribution of each interface to the voltage loss could be quantified. This allowed for a targeted improvement of the limiting interface. For p-i-n CsPbI2Br perovskite solar cells, a lithium fluoride interlayer between the perovskite and the CTL C60 improved the energy level alignment and decreased the defect density at the interface. Even though the VOC was improved by 110mV, a strong mismatch between quasi-Fermi level splitting (QFLS) and VOC remained. The perovskite/C60 interface was also found to limit the efficiency of p-i-n DMAI-CsPbI3 perovskite solar cells. A surface treatment of the perovskite layer using 1,4-butanediamine (DAB) improved this interface, removing the QFLS−e ·VOC mismatch. In combination with a passivation layer consisting of the fluorinated sodium molecule F-Na, the limitation of the perovskite/C60 interface could be overcome, and the VOC and fill factor could be substantially increased. These targeted improvements resulted in p-i-n DMAI-CsPbI3 perovskite solar cells with a PCE of 20.05%. A comparative loss analysis showed that the voltage loss is almost as low as in state-of-the-art triple-cation perovskite solar cells, but the perovskite/C60 interface needs further improvement. Measurements on CsPbI2Br and DMAI-CsPbI3 perovskite solar cells revealed one order of magnitude higher ion densities and one to two orders of magnitude lower mobilities than in organic-inorganic perovskite solar cells. Mobile ions were found to decrease the PCE, most likely by accumulating at the interfaces, screening the internal field and therefore increasing non-radiative recombination. Even though the ion densities were similar, this decrease in PCE was lower in DMAI-CsPbI3 perovskite solar cells as compared to CsPbI2Br perovskite solar cells. This suggests that the more effective interface passivation in DMAI-CsPbI3 perovskite solar cells can decrease the non-radiative recombination at the interface even at high ion densities, resulting in a lower hysteresis. These results addressed the main challenges for inorganic perovskite solar cells and presented new potential top cells for silicon-perovskite tandem solar cells.

Author dc:creator

• Grischek, Max

Advisor dc:contributor.advisor

• Albrecht, Steve

Licence dc:rights.uri

• https://creativecommons.org/licenses/by-nc/4.0/

Language dc:language.iso

en

Identifier URI

https://doi.org/10.14279/depositonce-20355

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/21555