Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic

Pedot

PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to

Pedot

PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells.

Organic-inorganic hybrid perovskite materials offer the potential for realization of low-cost and flexible next-generation solar cells fabricated by low-temperature solution processing. Although efficiencies of perovskite solar cells have dramatically improved up to 19% within the past 5 years, there is still considerable room for further improvement in device efficiency and stability through development of novel materials and device architectures. Here we demonstrate that inverted-type perovskite solar cells with pH-neutral and low-temperature solution-processable conjugated polyelectrolyte as the hole transport layer (instead of acidic

Pedot

PSS) exhibit a device efficiency of over 12% and improved device stability in air. As an alternative to

Pedot

PSS, this work is the first report on the use of an organic hole transport material that enables the formation of uniform perovskite films with complete surface coverage and the demonstration of efficient, stable perovskite/fullerene planar heterojunction solar cells.

A series of semi-crystalline, wide band gap (WBG) photovoltaic polymers were synthesized with varying number and topology of fluorine substituents. To decrease intramolecular charge transfer and to modulate the resulting band gap of D-A type copolymers, electron-releasing alkoxy substituents were attached to electron-deficient benzothiadiazole (A) and electron-withdrawing fluorine atoms (0-4F) were substituted onto a 1,4-bis(thiophen-2-yl)benzene unit (D). Intra- and/or interchain noncovalent Coulombic interactions were also incorporated into the polymer backbone to promote planarity and crystalline intermolecular packing. The resulting optical band gap and the valence level were tuned to 1.93-2.15 eV and -5.37 to -5.67 eV, respectively, and strong interchain organization was observed by differential scanning calorimetry, high-resolution transmission electron microscopy and grazing incidence X-ray scattering measurements. The number of fluorine atoms and their position significantly influenced the photophysical, morphological and optoelectronic properties of bulk heterojunctions (BHJs) with these polymers. BHJ photovoltaic devices showed a high power conversion efficiency (PCE) of up to 9.8% with an open-circuit voltage of 0.94-1.03 V. To our knowledge, this PCE is one of the highest values for fullerene-based single BHJ devices with WBG polymers having a band gap of over 1.90 eV. A tandem solar cell was also demonstrated successfully to show a PCE of 10.3% by combining a diketopyrrolopyrrole-based low band gap polymer.