Book excerpt: Smartwatch? Fitness tracker? Portable ECG? Smartphone? Posture monitor? Hearing aid? MP3 player? E-reader? Wireless headset? Hiking watch? Gaming headset? Sleep monitor? Laptop computer? Tablet? Indeed, a dizzying array of portable and wearable electronic devices is available to the modern consumer. Not surprisingly, as the number of devices an individual chooses to wear or carry increases so does the energy required to power those devices. Judging by the increasing popularity of portable power banks, waiting to recharge many of these devices using standard wall outlets is no longer a standard practice. Wearable Solar Cell Systems looks at the possibilities for supporting the energy demand of these devices without the need to return to the dreaded wall outlet for recharging. While crystalline silicon dominates world markets, second- or third-generation solar cell technologies may be more suitable to wearable systems. Array size, architecture, and management must also be chosen to best serve portable and wearable devices and harvest light energy from different light sources under a broad range of input conditions. This book is intended to serve a wide audience from students who desire a basic introduction to solar (photovoltaic) cell technology to professionals seeking a holistic picture of wearable solar cells and systems.