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Wide bandgap polymer donor PM6 and narrow bandgap polymer acceptor PY-IT were selected to construct all-polymer solar cells (all-PSCs) with a layer-by-layer (LbL) or bulk heterojunction (BHJ) structure. The solvent additive 1-chloronaphthalene (CN) plays a vital role in improving the performance of all-PSCs. The power conversion efficiency (PCE) of LbL all-PSCs is improved to 15.81% from 13.67% by incorporating 1 vol% CN in PY-IT solution, benefiting from the simultaneously enhanced short circuit current density (JSC) of 22.61 mA cm−2 and fill factor (FF) of 73.62%. A similar phenomenon is also observed in BHJ all-PSCs whose PCE increased from 13.29% to 15.29% by incorporating 1 vol% CN in PM6:PY-IT blend solution, originating from the optimized phase separation for better exciton dissociation and charge transport in the BHJ active layers. Over 15% PCE improvement can be obtained in the BHJ and LbL all-PSCs by incorporating appropriate additive CN as a morphology regulator. It should be noticed that the PCEs of LbL all-PSCs with CN are higher than those of other all-PSCs, indicating that the LbL processing method combined with the additive should be a prospective strategy to fabricate highly efficient all-PSCs. [ABSTRACT FROM AUTHOR]

Layer-by-layer polymer solar cells (LbL-PSCs) were prepared with PNTB6-Cl as the donor and Y6 as the acceptor by a sequential spin-coating method. Two solvent additives DPE and DFB were individually incorporated into PNTB6-Cl chlorobenzene solution and Y6 chloroform solution. A PCE of 17.53% was achieved for the optimal LbL-PSCs with two solvent additives, which is much larger than the PCE of 16.38% for the LbL-PSCs without solvent additives. Over 7% PCE enhancement can be realized by individually employing solvent additives in donor and acceptor layers, resulting from the simultaneously enhanced open circuit voltage (VOC) of 0.88 V, short circuit current density (JSC) of 26.63 mA cm−2 and fill factor (FF) of 74.83%. The photogenerated exciton distribution, charge transport and collection in the LbL-PSCs can be optimized by employing different solvent additives in donor and acceptor solutions. Meanwhile, the efficient energy transfer from PNTB6-Cl to Y6 can provide an additional channel for improving the exciton utilization efficiency through exciton dissociation at PNTB6-Cl/Y6 interfaces. Meanwhile, the PCEs of LbL-PSCs are better than those of bulk heterojunction PSCs with the same materials and solvent additives, indicating the great potential of LbL-PSCs for commercial application. [ABSTRACT FROM AUTHOR]

Amplified spontaneous emission (ASE) has become a common phenomenon in hybrid perovskites by establishing coherent light-emitting excitons. This paper reports a new phenomenon that the long–range orbit–orbit interaction is established through orbital polarizations between coherent light-emitting excitons during the generation of ASE in the CsPbBr3 microrods. Essentially, when the orbital polarizations are optically generated with the same direction between coherent light-emitting excitons by using a circularly polarized pumping beam, the ASE amplitude can be largely enhanced by 22.3%, as compared to the situation when the orbital polarizations are generated with opposite directions by using linearly polarized photoexcitation in randomly orientated microstructures. This observation provides evidence that long–range orbit–orbit interaction occurs between coherent light-emitting excitons in ASE. Furthermore, the long–range orbit–orbit interaction between coherent light-emitting excitons is simultaneously increased with the ASE amplitude while increasing the pumping fluence. Therefore, the long–range orbit–orbit interaction plays an important role in developing coherent light-emitting excitons towards ASE in metal halide perovskites. [ABSTRACT FROM AUTHOR]