Laporte-Rule-Guided Molecular Symmetry Control of NIR-Selective Organic Semiconductors for Colorless and Transparent Photovoltaics

Abstract

Near-infrared (NIR)-selective organic photovoltaics (OPVs), which harvest NIR photons while remaining transparent in the visible region, offer a promising platform for colorless and transparent solar cells. However, it remains difficult to design molecules that simultaneously possess NIR-selective absorption and the semiconductor characteristics required for OPV operation. Here, we combine Laporte-rule-guided control of molecular symmetry with intramolecular charge-transfer engineering using a strongly electron-donating indacenodipyrrole unit to develop an acceptor–donor–acceptor molecule P1 with absorption extending into the NIR region. Theoretical calculations predict that the dominant allowed transition of P1 is to the first excited state, whereas transitions to higher excited states are largely suppressed. Consistent with this, P1 selectively absorbs in the NIR region with negligible visible absorption, yielding a colorless and transparent appearance. The frontier-orbital energetics and excitonic parameters of P1 are suitable for NIR-selective photoelectric conversion. Notably, single-component OPVs based on P1 achieve external quantum efficiencies exceeding 15% in the NIR region while retaining high visible transparency. Time-resolved measurements further confirm effective carrier generation and charge transport under NIR photoexcitation. These results demonstrate that orbital-symmetry control can suppress visible absorption while charge-transfer-induced bandgap narrowing enables NIR photoresponse, offering a molecular design principle for colorless wavelength-selective organic optoelectronic devices.