Inorganic semiconductor-based broadband photodetectors are ubiquitous in imaging technologies such as digital cameras and photometers. Herein a broadband organic photodiode (OPD) that has performance metrics comparable or superior to inorganic photodiodes over the same spectral range is reported. The photodiode with an active layer comprised of a poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]:[6,6]-phenyl-C71-butyric acid methyl ester bulk heterojunction blend had a dark current < 1 nA/cm2, specific detectivity of ~1013 Jones, reverse bias -3 dB frequency response of 100 kHz to 1 MHz, and state-of-the-art Linear Dynamic Range for organic photodiodes of nine orders of magnitude (180 dB). The key to these performance metrics was the use of a thick junction (700 nm), which flattened the spectral response, reduced the dark current and decreased performance variations. The strategy also provides a route to large area defect free "monolithic" structures for low noise integrated photo-sensing, position determination, or contact, non-focal imaging. Organic photodiodes with spectrally flat photo-responses are realized using a thick bulk heterojunction with dark current <1nA/cm2, state-of-the-art Linear Dynamic Range of 180 dB, specific detectivity of ~1×1013 Jones and frequency response of 100 KHz to 1 MHz. The performance metrics are comparable or superior to inorganic photodiodes over the same spectral range. The strategy provides a route to large area defect free "monolithic" light sensing devices.