Efficient and UV-stable perovskite solar cells enabled by side chain-engineered polymeric hole-transporting layers

Biaxially-extended octithiophene-based conjugated polymers are demonstrated as effective polymeric hole-transporting layers (HTLs) to simultaneously enhance the efficiency and UV-photostability of perovskite solar cells (PVSCs). The intense UV absorption contributed from the conjugated side-chain groups of such polymers facilitated its function of UV filtering when serving as the bottom HTL in PVSCs. Through rationally tailoring polymer backbone structure, a highly efficient (PCE: 18.34%) PVSC with much improved UV-photostability and ambient stability was successfully achieved.