of physiological signals. Energy harvesting from ambient energy sources that prevent the need to charge or recharge a battery offers an excellent path for self-power functionality. Many groups have demonstrated self-powered biomedical devices using environmental sources such as ambient light with solar cells, [1][2][3][4][5] body heat with thermoelectric devices, [6][7][8][9][10][11] and motion with triboelectric [12][13][14][15][16][17] or piezoelectric devices. [18][19][20][21][22] In particular, tapping into solar energy through photovoltaics (PV) has demonstrated many advantages such as easy deployability, [23][24][25][26] and sufficient energy density [27] to meet the energy demands of wearable electronics for long-term usage. Various solar cell technologies have been implemented on autonomous devices such as arm bands, [23] electrocardiogram (ECG) devices, [24,25] and wearable global positioning system (GPS) tracking devices. [26] However, there are several challenges in today's solar cells that hamper their use as viable energy sources for wearable applications. Unlike the conventional operation of solar cells under actual one sun irradiation conditions, wearable usages typically require indoor operation which has much weaker light intensity (≈0.44 mW cm −2 ). [28] However, the efficiencies of most solar cell technologies are limited at low light illumination and thus reducing the energy autonomy for indoor applications. It is therefore challenging to drive sensing systems that are complicated or have high power consumption in an indoor light (for example, fluorescent lamp) environment. Under the typical outdoor illuminating condition, there is a higher density of photogenerated charge carriers, and hence most of the electronic disorders, defects, or trap sites that are present in the solar cell can be filled easily. However, the density of photogenerated carriers is significantly reduced under indoor ambient lighting condition and thus the density of defects or trap sites cannot be filled efficiently, leading to shunting effects and substantial power loss of the PV devices.Specifically, the open-circuit voltage (V oc ) drops severely under low light illumination (< 1-10 mW cm −2 ), which limits the driving capability and reliability for the power source. [29][30][31] Furthermore, for indoor light-harvesting, it is essential to note that the spectral content provided by light-emitting diodes (LEDs) or Wearable sensors and electronics for health and environment monitoring are mostly powered by batteries or external power supply, which requires frequent charging or bulky connecting wires. Self-powered wearable electronic devices realized by integrating with solar cells are becoming increasingly popular due to their ability to supply continuous and long-term energy to power wearable devices. However, most of the solar cells are vulnerable to significant power losses with decreasing light intensity in indoor environment, leading to an errant device operation. Therefore, stable autonomous energy in a reliable a...