The interfacial properties of organolead halide perovskite solar cells (PSCs) affect the exciton and charge-transport dynamics significantly. Thus, proper modification of the interfaces between perovskite and charge-transport layers is an efficient method to increase the power conversion efficiency (PCE) of PSCs. In this work, we explore the effect of a nonionic surfactant, that is, Triton X-100 (TX) additive, in the poly­(3,4-ethylenedioxythiophene)-poly­(styrenesulfonate) (PEDOT:PSS) hole-transport layer. The electronic structure of TX-modified PEDOT:PSS is investigated with ultraviolet/X-ray photoelectron spectroscopy and X-ray absorption spectroscopy with various TX concentrations. The surface of the TX-modified PEDOT:PSS layer showed high TX content, and thus the semimetallic properties of PEDOT:PSS were suppressed conspicuously by its insulating nature. With the TX-modified PEDOT:PSS, the PCE of methylammonium lead iodide (MAPbI3) PSCs increased significantly. To elucidate the origin of the improved device performance, the electrical properties and photoluminescence were investigated comprehensively. Consequently, it was found that the TX additive inhibits interface recombination between PEDOT:PSS and MAPbI3, which is caused by the suppression of semimetallic properties of the PEDOT:PSS surface. Hence, we fabricated flexible PSCs successfully using a graphene electrode and TX-modified PEDOT:PSS.

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The optical properties of the Stranski–Krastanov (S–K) grown InAs/GaAsSb quantum dots (QDs) coupled to sub-monolayer (SML) InAs QD stacks are investigated using photoluminescence (PL) spectroscopy. The PL emission peak of the S–K QDs shifts to shorter wavelengths with increasing the number of SML stacks (NSML) due to the increasing strain fields from the SML QDs. The PL peak energy is linearly increased with increasing the cube root of excitation power, with a different ratio of the absorption coefficient to radiative recombination rate for all the QD samples. The total carrier lifetime for the S–K QDs is increased with increasing NSML, most probably caused by the increase in the ground-state transition energy of the S–K QDs. The nonmonotonic behavior of the thermal activation energy of electrons in the S–K QDs is observed due to the NSML-dependent variation of the strain and Coulombic interaction within the QDs.

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