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The strong aggregation of Poly(3-hexylthiophene) (P3HT) severely limits its use as the hole-transport material in emerging quantum dot photodetectors and photovoltaics. Herein, we propose a facile and cost-effective strategy to control the solution-state aggregation of hole transporting layers by designing a dual polythiophene blend based on P3HT and its alkylthio-substituted analogue named Poly(3-hexylthiothiophene) (P3HTT). In our photodetector device, we have used the dual polythiophene as the hole transport layer and achieved a specific detectivity (D*) on the order of 1012 Jones. In particular, by incorporating a small amount of P3HTT into the dual polythiophene mixture, we observed a remarkable 28% performance enhancement. This study provides a comprehensive analysis of the solution structure of the dual polythiophene blend, elucidates the evolution of the condensed matter structure, and ultimately presents a promising avenue for enhancing the performance of low-cost quantum dot photodetectors. [ABSTRACT FROM AUTHOR]

The degradation of archetype organic photovoltaics comprising both vacuum and solution-deposited bulk heterojunction active regions is investigated and quantified using a theory based on detailed balance, which relates the open-circuit voltage to the efficiency of charge transfer state emission. To describe this relationship, we account for the difference between electroluminescent external quantum efficiency and the charge transfer emission efficiency. An empirical factor, m, is introduced to distinguish between nonradiative defect sites both within, m = 1, and outside, m >1, of the photoactive heterojunction. The m-factor is used to determine the primary sources of degradation for archetype solution- and vacuum-processed material systems. We conclude that degradation occurs primarily within the donor–acceptor heterojunction for the vacuum-processed devices (where m = 1.020 ± 0.002) and outside of the photoactive heterojunction for the solution-processed devices studied, both with and without an anode buffer layer (where m = 2.93 ± 0.09 and m = 1.90 ± 0.01, respectively). [ABSTRACT FROM AUTHOR]