  Solar batteries capable of harvesting sunlight and storing solar energy
present an attractive vista to transition our energy infrastructure into a
sustainable future. We present an integrated, fully earth-abundant solar
battery design based on a bifunctional (light absorbing and charge storing)
carbon nitride (K-PHI) photoanode, combined with all-organic hole transfer and
storage materials. An internal ladder-type hole transfer cascade via a hole
transport layer is used to shuttle the photogenerated holes to the PEDOT:PSS
cathode. This concept differs from previous designs such as light-assisted
battery schemes or photocapacitors and allows charging with only light or
light-assisted during electrical charging and discharging, thus substantially
increasing the energy output of the cell. Compared to battery operation in the
dark, light-assisted (dis)charging increases charge output by 243 %, thereby
increasing the electric coulombic efficiency from 68.3 % in the dark to 231 %,
leading to energy improvements of 94.1 % under illumination.
