Absorption-induced external quantum efficiency modulation in organic nanocrystals incorporated organic solar cells

The various loss mechanisms lead to low power conversion efficiency in organic photovoltaics. One of the main limitations is insufficient spectral coverage, to overcome this loss mechanism various methodologies were adopted. In this work, NS1 small molecule nanocrystals has been introduced in conventional P3HT:PC₇₀BM binary system to study its effects on spectral response and photovoltaic performance. Introduction of NS1 nanocrystal improve cascaded energy level alignment between donor and acceptor semiconductors and provide well-aligned energy level, results in enhanced fill factor. The variation of V_oc was seen with respect to polymer and NS1 ratio. Influence of optoelectronic properties of photoactive layer and photovoltaics parameters were analyzed detailly. At incorporation of optimized NS1 ratio, charge transfer process between P3HT and PC₇₀BM improved and reduced recombination was seen. Composition-dependent PV parameter was investigated and discussed detailly. Host organic semiconductor nanocrystal in polymer photoactive layer favors the complementary optical absorption of forbidden absorption region of P3HT. This process was confirmed by external quantum efficiency and lowered leakage current. It is noted that UV visible spectrum trend was noted in the external quantum efficiency measurement. This work suggests that utilizing organic small molecule nanocrystal with optimized ratio will enable optical absorbance throughout the visible region. Further study would give enhanced performance attributed by widened spectral response.