Bifunctionally Driven Organic Photonic Conversion Devices Facilitated by Minimalistic Synthesis-Based Interfacial Energetic Alignment

Bifunctional integration of indoor organic photovoltaics (OPVs) and photodetectors (OPDs) faces fundamental challenges because of incompatible interfacial thermodynamics: indoor OPVs require unimpeded charge extraction under low-light conditions (200–1000 lx), whereas OPDs require stringent suppression of noise current. Conventional hole transport layers (HTLs) fail to satisfy these opposing charge-dynamic requirements concurrently with commercial practicality (large-area uniformity, photostability, and cost-effective manufacturability). This study introduces benzene-phosphonic acid (BPA)—a minimalist self-assembled monolayer (SAM)-based HTL with a benzene core and phosphonic acid anchoring group—enabling cost-effective synthesis and excellent ITO interfacial properties such as energy alignment, uniform monolayer, and stability. This molecular design resolves core limitations and achieves high indoor OPV efficiency (28.6% PCE at 1000 lx LED 2700 K), maintains 93% PCE retention when scaled by ≈220× area, and delivers competitive self-powered (V = 0 V) OPD performance (noise equivalent power = 584 fW at bandwidth = 1 Hz and wavelength = 730 nm; 3 dB frequency = 103 kHz). Simplified synthesis of BPA reduces production costs by 720% ($0.042 cm⁻²) and achieves 9× higher power-per-cost ratio (19.25 mW∙$⁻¹) relative to its counterpart SAM. Synergy between performance and commercial practicality positions BPA-HTL as a transformative enabler for self-powered IoT and wearable optoelectronics.