Influence of the additives in poly(3-hexylthiophene) hole transport layer on the performance of perovskite solar cells

The hybrid organic-inorganic methylammonium lead trihalide (CH3NH3PbI3-xClx) perovskite solar cells employing poly(3-hexylthiophene) (P3HT) hole transport layer with different doped amounts of bis(trifluoromethane) sulfonimide lithium salt (Li-TFSI) and 4-tert-butylpyridine (D-TBP) are fabricated. It is found that the doped amounts of Li-TFSI and D-TBP greatly affect the performance of the devices, such as surface coverage, Hall mobility and bulk concentration of P3HT films. The highest power conversion efficiency of 9.7% is obtained in optimal devices due to the enhanced charge transport and the reduced charge recombination at the interfaces of the devices. The best efficiency of the optimal devices with Li-TFSI and D-TBP is increased by ~90%, compared with the reference without additives.